Surface texture hot rolled asphalt (Sand patch test)
Validation of results
By using a UKAS accredited testing organisation results will be accepted by all UK Government agencies, including Highways England and local authorities.
BS EN 13036-1: 2010 and Specification for Highway Works Cl 921 (Glass beads).
Hot rolled asphalt service
Both Highways England and all local authorities require proof of compliance of the texture depth produced with the installation of a hot rolled asphalt surface course. This is an indirect method of assessing the skidding resistance. The correct application and compaction of the pre-coated chipping is of critical importance. In particular, the embedment and distribution of the chippings contribute to the road’s acceptability.
The hot rolled asphalt must be fully compliant with the specification and laid at the correct thickness and temperature. The pre-coated chippings must comply with the grading and coverage requirements, as well as the flakiness index and size and shape specifications. The chips must be dust free and free flowing when added to the hopper of the chipper.
Chipping application & compaction temperature
Chipping application and compaction is vitally important. This should be done as soon as possible after the asphalt is laid and should be completed before the asphalt reaches the minimum rolling temperature. Wherever possible a mechanical chipping spreader should be used, with the spread rate adjusted according to the weather conditions. Over-rolling will result in the chips being pushed too far into the asphalt matrix resulting in low texture depth. Too little or cold rolling will not embed the chips sufficiently resulting in a too high texture depth. Additionally, the chippings will pluck out when trafficked.
The sand patch test will be adversely affected by wet weather. Avoid testing in rainy conditions or when the asphalt is still wet from rolling. Always ensure the technician carrying out the tests is competent.